Method and system for agglomerating chopped fiber strand and product

ABSTRACT

A new system and method for making agglomerates of chopped glass fiber strand segments is disclosed as are the agglomerates produced. The agglomerates, made by feeding wet chopped fiber strand segments into a wave chamber having a vibrating curved surface that produces a wave-like flow pattern in the segments and agglomerates, have a substantially higher bulk density and greatly improved flow characteristics than conventional chopped strand reinforcements. The wet agglomerates are usually dried in any conventional dryer.

This application is a continuation of, and claims priority benefit under35 U.S.C. §120 to, parent U.S. patent application Ser. No. 11/149,162,filed Jun. 10, 2005, which is a continuation of, and claims prioritybenefit under 35 U.S.C. §120 to, parent U.S. patent application Ser. No.10/291,322, filed Nov. 8, 2002, the contents of which is incorporated byreference herein for all purposes.

This invention includes a method and system for agglomerating wetchopped glass, polymer, etc. fiber strand segments into pieces that aredenser and more free flowing than normal chopped strand. The resultantproduct is useful in processes for making fiber reinforced plastics andin processes for making other fiber containing products.

Chopped strand reinforcement products such as chopped strand forthermoplastics are typically made by pulling fibers from a plurality offiberizers while the material is in a molten state, cooling the fibers,coating the fibers with water and a chemical sizing, gathering thefibers into strands, chopping the strands into segments of desiredlengths and drying the wet chopped strands in a vibrating flatbed ovenand sorting the resultant dry chopped strand to remove undesirable lumpsand fuzz. A typical process can be seen in U.S. Pat. No. 3,996,032.These types of processes produce chopped strand segments having a widerange of diameters and containing a wide range of numbers of fibers,e.g. from just a few fibers to 4000 or more fibers per segment.

Hundreds of millions of pounds of chopped strand products have beenproduced in the above described processes and while these productsworked well in making fiber reinforced products of a wide variety.However, for several years there has existed a desire for a product thathas a higher density, flows better through small openings in cone shapedbins and feeders and that contains fewer small diameter segments thattend to produce fuzz balls in the customers system.

Several processes have been disclosed for pelletizing or agglomeratingchopped strand. These include U.S. Pat. Nos. 3,984,603, 4,107,250,4,164,534, 4,840,755, 5,002,827, 5,185,204, 5,269,993, 5,578,535,5,585,180, 5,639,807, 5,693,378, 5,868,982, 5,945,134 and WO 01/05722.While at least one of these processes produces chopped strandreinforcement segments that meet most or all of the desiredimprovements, there are still system and process improvements andefficiencies desired such as less costly, simpler and lower operatingcost systems and processes.

SUMMARY OF THE INVENTION

The present invention includes a system and method for makingagglomerated reinforcing fiber strand segments, such as agglomeratedchopped strand for reinforcing plastics and products made by the method.The system comprises a chopper for chopping one or a plurality of wetstrands of fibers having a chemical sizing on the circumferentialsurfaces of the fibers into segments, and agglomerator and a dryer fordrying agglomerates of wet chopped strand segments, the improvementbeing an agglomerator comprising a non-rotating wave chamber having agenerally horizontal, non-rotating, elongated, vibrating curved surface,working surface, for contacting the wet chopped strand segments, theworking surface being generally concave in cross section in a planeperpendicular with the length of the working surface. The term “wavechamber” designates the type of action that the working surface producesin the chopped strand segments and agglomerates, moving the materialupward on the working surface like an ocean wave and curling it over thetop to slide back downwardly inside the chamber to the working surfacewhere the wave action is repeated again and again until the agglomeratesexit the wave chamber.

By generally horizontal is meant horizontal plus or minus up to about 10degrees. Preferably the working surface declines from an upstream end toa downstream end by a variable amount up to about 6 degrees. Bynon-rotating is meant that the wave chamber does not rotate a fullrevolution, preferably doesn't rotate more than 180 degrees and mostpreferably doesn't rotate more than about 10 degrees. The preferredembodiments disclosed herein rotate, if at all, only due to theamplitude of vibration and spring action and any rotation is reciprical,i.e., back and forth. By generally concave surface is meant that theworking surface in cross section can have a constant radius or achanging radius of two or more radii. By wave action is meant a type ofaction similar to a breaking wave.

Preferably, but not necessarily, the contacting or working surface has atextured or non-stick surface to reduce tendency of the wet choppedstrand segments to stick to said surface and to aid in achieving a waveaction in the chopped strand segments and agglomerates. The frequencyand/or amplitude of vibration can preferably be varied to produce andoptimize the wave like movement of the wet chopped strand segments andagglomerates.

Preferably the dryer is a vibrating, flat bed dryer known for drying wetchopped strand segments. The system can have additional equipment at thedryer's downstream end or downstream of the dryer for sorting theagglomerated chopped strand segments to remove oversize and undersizepieces. The system can also have conveyor means for collecting the wetchopped strand segments from the chopper and delivering said segments tothe vibratory wave chamber.

The method of the present invention includes chopping one or a pluralityof strands of wet fiber into chopped strand segments, the segments alsocontaining a chemical sizing on circumferential surfaces of the fibers,forming the wet segments into agglomerates and drying the agglomeratesto form agglomerates of chopped fiber strands, the improvementcomprising forming agglomerates by subjecting a layer of the wet choppedstrand segments to vibration against the generally concave workingsurface of an elongated curved surface, the working surface comprisingat least about a 60 degree arc circle with at least about 45-60 degreesof the arc being on one side of an imaginary vertical line extendingthrough the lowest point on the working surface and the remainder, ifany, lying on the opposite side of the vertical line. Preferably, thefrequency and/or amplitude of the vibrators can be changed to optimizethe wave action and quality of agglomerates at different feed ratesand/or with different size or type of chopped strand segments. The frontto exit of the vibrating curved surface can be declined to affect theretention time the segments and agglomerates are in the wave chamber andthe capacity of the wave chamber.

The general appearance of the agglomerates in shape and size is similarto that of wild rice or grains of wheat. The agglomerates are about ⅛ toabout ½ inch long and typically about ⅛ to about ¼ inch long. Thediameter of the agglomerates can vary and can be changed to address theneeds of different applications, but typically are less than about3/16-¼ inch in diameter. The agglomerates of chopped fiber strandsegments produced by the system and method of the invention havesubstantially reduced fuzz content and segments of only a few fibers.The agglomerates have substantially improved density and flowcharacteristics compared with conventional, non-agglomerated, drychopped strand products, and equal or improved performancecharacteristics as reinforcements in various plastics and othermatrices. Agglomerates run through conventional sorting devices toremove fuzz clumps, fines or lumps are further improved a small amount,because the agglomeration tends to eliminate fines and fuzz and theabove method and system produces hardly any oversized lumps.

When the word “about” is used herein it is meant that the amount orcondition it modifies can vary some beyond that so long as theadvantages of the invention are realized.

Practically, there is rarely the time or resources available to veryprecisely determine the limits of all the parameters of ones inventionbecause to do would require an effort far greater than can be justifiedat the time the invention is being developed to a commercial reality.The skilled artisan understands this and expects that the disclosedresults of the invention might extend, at least somewhat, beyond one ormore of the limits disclosed. Later, having the benefit of the inventorsdisclosure and understanding the inventive concept and embodimentsdisclosed including the best mode known to the inventor, the inventorand others can, without inventive effort, explore beyond the limitsdisclosed to determine if the invention is realized beyond those limitsand, when embodiments are found having no further unexpectedcharacteristics, the limits of those embodiments are within the meaningof the term about as used herein. It is not difficult for the artisan orothers to determine whether such an embodiment is either as expected or,because of either a break in the continuity of results or one or morefeatures that are significantly better than those reported by theinventor, is surprising and thus an unobvious teaching leading to afurther advance in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a prior art system for making agglomerates ofwet chopped strand.

FIG. 2 is a front view of a system for making agglomerates of wetchopped strand in accordance with the present invention.

FIG. 3 is a front view of one device for agglomerating chopped strandsegments in accordance with the present invention.

FIG. 4 is an exit end view of the device shown in FIG. 3 with the endcap with exit port removed to see the agglomerates.

FIG. 5 is a cross section of a wave chamber of another agglomeratingdevice suitable for the invention.

FIG. 6 is a cross section of a wave chamber of still anotheragglomerating device suitable for the invention.

FIG. 7 is a cross section of a wave chamber of yet another agglomeratingdevice suitable for the invention.

FIG. 8 is a partial cross section of the wave chamber shown in FIGS. 3and 4 and shows a working surface producing the wave like action thatagglomerates chopped strand segments in the present invention.

FIGS. 9 and 10 show optional working surfaces having two or more radii.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a prior art system used to manufacture agglomerated choppedstrand products with different process portions labeled as A, B, C andD. Portion A is the fiber forming part of the system. Portion B is thechopping part of the system. Portion C is the agglomerating part of thesystem and portion D is the drying, sorting and packaging part of thesystem.

Fibers 1, such as glass or polymer fibers, are formed by passing themolten form of the material through nozzles 2 in the bottom of bushings4, fiberizers, in a known manner and the fibers 1 are pulled rapidly toattenuate the fibers to the desired diameter and to quickly cool thefibers 1 with air to below their softening point. A fine mist of wateris sprayed on the fibers to help cool them and the fibers 1 are rapidlypulled into contact with the roller of a chemical sizing applicator 6where the surfaces of the fibers are coated with any one of numerouschemical sizings. The sizings are usually water based and typicallycontain a resinous film former, a silane and one or more surfactants orwetting agents, cross linkers etc. The type of sizing used is determinedby the type of polymer or other matrix that the fibers will be used toreinforce as is well known. The present invention is applicable to abroad range of sizing compositions. The sizing composition is not a partof the present invention but rather the present invention is applicableto many known sizings.

The chemically coated, wet fibers are next pulled around a groovedpulley 8 that gathers all of the fibers 1 from the bushing 4 into asingle strand 9. The fiber strands 9 can contain any number of fibersfrom a few hundred to more than 4000. The fibers 1 and the fiber strands9 are usually pulled at the desired speed by the chopper in part B ofthe system, which in this case is a chopper 10. The strands 9 may bepulled over a strand guide roll 11 that keeps individual strands 9separated. Chopper 10 is a known fiber strand chopper comprising abackup roll 12, a blade roll 13, a knurled idler roll 14, a strandmoving finger 15, a strand starting roll 16, a roll starting switch 17,and a new strand grooved roll, 18. The chopper 10 and its operation aredisclosed in detail in U. S. Pat. No. 6,148,640, the disclosure of whichis hereby incorporated herein by reference.

The chopper 10 separates the fiber strands 9 into segments 19 of desiredlength. The fiber strand segments 19 are collected on a belt conveyor 22and transported to part C of the prior art system, which is anagglomerator for chopped strand segments 19. The agglomerator 24 shownhere is disclosed in detail in U.S. Pat. No. 5,945,134 and thereforewill not be described further here. Other devices for agglomerating orpelletizing chopped strand segments have been disclosed in other U.S.patents such as U.S. Pat. Nos. 3,984,603, 4,107,250, 4,164,534,4,840,755, 5,002,827, 5,185,204, 5,269,993, 5,578,535,5,639,807,5,693,378, 5,585,180, 5,868,982, however many of the devicesand methods disclosed in these additional patents have not always metall of the current requirements of the customers for agglomeratedchopped strand products, or have been costly to operate for making glassand/or polymer fiber segments.

Following agglomeration, the agglomerated chopped strand agglomerates 26(agglomerates), which are still wet, must be dried. This is accomplishedby feeding the agglomerates 26 into part D, a dryer. Many types ofdryers have been used and one of the frequently used dryers is avibrating fluid bed dryer 28. This type of dryer 28, also used to drychopped fiber strand segments 20 to form conventional chopped strandreinforcement products, transports the agglomerates 26 on or above aperforated flat bed 30. The transporting force is supplied by aneccentric motor 30 acting on the dryer 28 which is mounted on springs32. The drying and suspension of the agglomerates 26 in the dryer 28 isaccomplished with hot air forced through ports 34 into a chamber 33 andon through perforations in the perforated flat bed 30 and a layer of theagglomerates 26 and finally through one or more exhaust stacks 35 in ahood 36 of the dryer 28. The chemical sizing in the agglomeratesprovides a weak bond in the agglomerates 26 that keeps them frombreaking apart with handling, but allows the fibers to break apart anddisperses in the plastic to which the agglomerates are later added.

The dry agglomerates 37 can be packaged immediately as they exit thedryer 28, or they can be run through an optional part E which is asorter screen of any of various known types, such as the inclined multideck sorter screen 38 comprising a top screen 40 to remove any lumps orclumps of fuzz that might be in the agglomerates through a side exit 39,a lower screen 42 which allows any fines in the dry agglomerates 37 topass through to a bottom chamber and funnel 44 to a scrap bin (notshown). The sorted agglomerates 37 pass out of the sorter screen andinto any package, such as a kraft board box 45. Known automaticpackaging equipment can be included in part E but is not necessary.

The known system described above produces acceptable agglomerated orpelletized chopped strand reinforcement products, but it is desirable tosimplify the agglomeration part of the system. The inventors havesurprisingly found that when wet chopped fiber strand segments arevibrated in a wave like action by an elongated vibrating curved workingsurface, the desired agglomeration takes place in a very simple devicewith no large rotating parts, reduced wearing surfaces and with lowenergy usage. The inventors have also found that a device well known formilling hard minerals and stone to fine powder surprisingly provides theabove described wave action needed to produce the desired agglomeratesfrom ordinary wet chopped fiber strand segments.

FIG. 2 shows the present inventive system. Parts A, B, D and theoptional part E are just like the prior art system shown in FIG. 1, butpart C, the wave chamber agglomerator 46 is a device that provides anelongated vibrating curved surface causing a wave like action describedabove which causes the wet chopped fiber strand segments 19 toagglomerate into wet, slightly flattened, shaped agglomerates 26 ofdesired size to form the desired agglomerated product 48. Typically, theagglomerates 26 will be about ⅛ inch to about ¼ inch long with themajority of the agglomerates having diameters of from about 0.06 inch toabout 0.2 inch, but longer agglomerates up to about ½ inch are suitablefor some applications. Preferably, at least 75 weight percent of theagglomerated product is in agglomerates of this diameter, morepreferably at least 85 weight percent and most preferably at least 90weight percent.

The method of agglomeration of the wet chopped strand segments 19 in theinventive system shown in FIG. 2 is the same as the method used with theconventional system shown in FIG. 1 except that the agglomeration takesplace on or near a non-rotating curved, vibrating surface instead of onor near a series of rotating curved surfaces. In the present inventionit is not necessary to add additional moisture or hydrating fluid to thechopped strand segments prior to agglomeration, nor is it necessary toadd a binder or second sizing composition to the wet chopped strandprior to agglomeration. The moisture content of the wet chopped fiberstrand coming from the chopper varies from about 10 wt. percent to about16 wt. percent. Generally, the greater the moisture content the fasterthe chopped strand will agglomerate and the larger will be theagglomerates with the same residence time and vibration frequency.Preferably the moisture content is within the range of 12-15 percent,and in production units of 36 inches inside diameter of the vibratingdrum or larger, the moisture content should not exceed about 15 wt.percent. When using a 36 inch diameter unit, the most preferred moisturecontent is in the range of about 12-13.5 wt. percent in the choppedfiber strand coming from the chopper and entering the wave chamberagglomerator.

Any vibrating elongated, concave, curved, surface is suitable foragglomerating the wet chopped strand segments 19. It is preferred thatthe non-rotating curved surface be a side of a cylinder or a segment orarc of a cylinder having a cross section of a circle, a portion of acircle, a semi-circle, or less than a semi-circle. However, curvedsurfaces having two or more radii are also suitable.

While a smooth inner curved surface is acceptable, it is preferred thatthe working surface be textured such as with small spaced apart dimples,ridges, X shaped or some other spaced apart raised forms to presentreduced contact which prevents sticking of the wet chopped strandsegments or partial agglomerates from sticking on the curved surface,yet providing a better gripping surface to enhance a lifting of thesegments and agglomerates up the curved surface to optimize the waveaction. Various “Toe Plates”, sized and formed into a curved surfacewith the raised texture on the concave surface, are suitable. Thepreferred material is stainless steel, but other metals coated withnon-corrosive coatings or various plastics, reinforced or not reinforcedwould also be suitable as would be various types of rubber known for usein wear resistant applications. A preferred dimpled material for theworking surface is 304 stainless (#4) 5.WL product available from theRigidized Metals Corp. of Buffalo, N.Y.

While the curved portion can be 360 degrees it need not be. A curvedportion containing about 210 degrees is suitable as are smallerportions, but the capacity might be reduced somewhat.

Surprisingly, one type of device found by the inventors to beparticularly suitable as the agglomerating device 46 in the presentinvention is shown in FIGS. 3 and 4. This type of device is availablefrom General Kinematics Corp. of Barrington, Ill. under the name ofVibra-Drum®, a device normally used as a milling or grinding device forstone and minerals.

A Vibra-Drum® 50 is shown in front view in FIG. 3 and in an end viewlooking at the exit end with a front panel removed in FIG. 4. The device50 is comprised of a generally horizontal cylindrical wave chamber 52(chamber) having a feed port 54 in an entrance end cap end and an exitport 56 at the bottom or 6 o'clock position on a downstream end cap 51.The wave chamber 52 can be of various diameters depending upon thecapacity desired and the length of the wave chamber. Generallyhorizontal means that the cylindrical wave chamber 52 can be horizontal,but preferably several degrees from horizontal such as less than 10degrees from horizontal. Diameters of about 2-3 feet are known to besatisfactory and it is believed that other diameters would also besatisfactory, such as 42 inch diameter or larger.

Normally the cylindrical wave chamber 52 will decline from an entranceend to an exit end. The angle of declination will affect the retentiontime of the wet chopped strand segments 19 and wet agglomerates 26 inthe cylinder 52 and preferably is adjustable. The chamber 52 has aworking surface 53 on its interior.

The chamber 52 is mounted on a frame piece 57A attached to one side ofthe chamber 52 and on a second frame piece 57B attached to an oppositeside of the chamber 52. The frame piece 57A is supported by an array ofcoil springs 58. The array of coil springs 58 comprises a plurality ofcoil springs 59, preferably arranged in two spaced apart and parallelrows. Each of the coil springs 59 are attached on their top ends 60 toan underside of the frame piece 57A. Bottom ends 61 of the coil springs59 are attached to the top of an elongated box like frame structure 62having a length at least as long as the length of an array of the coilsprings 58.

Mounted on opposite sides of said structure 62 and generally straddlingan end-to-end vertical imaginary centerline of said structure 62 are twoeccentric vibrators 64. The structure 62 and pair of vibrators 64 aresupported on an underneath side by two pairs of coil springs 65. Eachpair of coil springs 65 is located close to each end of the box channelmember 62 as shown in FIG. 3. The two pairs of coil springs 65 areattached on their lower ends 67 to a frame 68. The frame 68 is comprisedof a bottom member or plate 70 with a foot 71 on the underneath side ateach corner of the bottom member 70 and two spaced apart upright legs 73attached to the top of the bottom member 70. The upright legs 73 can bespaced apart about as much as the two pairs of coil springs 65 with eachleg 73 being aligned with each coil spring in the pair of coil springs65, but spaced apart such that each of the legs 73 is on the oppositeside of the bottom member 70 from the pair of coil springs 65 it isaligned with.

The second frame piece 57B is supported on its bottom side by at leasttwo spaced apart coil springs 75 with the top 76 of each coil spring 75being attached to the underneath side of the frame piece 57B and thebottom 77 of each coil spring 75 being attached to the top 78 of oneupright leg 73. The upright legs 73 can be further supported by armbraces 79 attached at one end close to an upper end of each leg 73 andat the other end to a spot on the upper side of the bottom member 70spaced from the upright leg 73 as shown in FIG. 4.

The generally horizontally wave chamber 52 is therefore totallysupported by coil springs which produce a wave like action on the wetchopped strand segments 19 that are fed through the feed port 54 andalso on the wet agglomerates 26 as they approach the exit port 56. Aparticular advantage of the VibraDrum® device shown above is thatbecause of the array of coil springs 58 located between the vibrators 64and said wave chamber 52, the vibrators 64 are smaller, requiring lesselectrical energy usage than if the vibrators were attached rigidly tosaid wave chamber 52. The wave chamber 52 on VibraDrum® equipment canarranged to be on either the right of the vibrators 64 or on the left,looking from the feed end, usually dictated by the orientation of theequipment feeding the chopped strand segments to the wave chamber 52.The unit shown in FIGS. 3-4 is a right hand unit. Vibrating wave chamberequipment are advantageous compared the tumbling devices used in thepast because they are easier to operate and maintain.

FIG. 4 shows a typical position of the wet agglomerates 26 and wetchopped strand segments 19 in an operating VibraDrum® with the arrayextending from about 5 o'clock to about 9 o'clock on the curved workingsurface 53. Thus, about 120 degrees of the curved surface inside thewave chamber 52 is a “working” surface and the remainder of the curvedsurface, at this feed rate, does not necessarily contact the wet choppedstrand segments 19 or the wet agglomerates 26 and therefore can bemodified in many ways. The feed rate will vary depending upon the sizeand length of the generally horizontal wave chamber. Also, even fewerdegrees of the curved surface will be a “working” surface at reducedfeed rates or if a longer wave chamber at greater declination is used.For example, as little as about 45-70 degrees of contact with theworking surface is suitable, as is about 45 to about 120 degrees, butabout 90 to about 100 degrees or about 90 to about 110 degrees ispreferred. A working surface of at least about 60 degrees with at leastabout 45 degrees being on a working side of a vertical centerlinerunning through the wave chamber is also suitable.

The important thing is to obtain a wave like movement inside the wavechamber, as shown in FIG. 8 on or adjacent a portion of a wave chamberhaving a working surface 53. The wet chopped fiber strand segments 19are moving in a wave like pattern as shown by the arrows, working theirway up the curved working surface 53 until they reach a maximum heightbased on the feed rate and the vibration frequency, then curling overand flowing down the inside over the upwardly moving segments 19 untilthey again contact the working surface 53 and repeat the pattern. Thisoccurs many times down the length of the wave chamber 52 until the nowagglomerates 26 reach the exit. Preferably one or more rubber damperssupplied by the manufacturer can be used between adjacent coils of oneor more of the coil springs if the vibrating tube tends to rock back andforth from side to side in operation.

At any given feed rate, the angle of declination of the wave chamber isadjusted to give the residence time needed to form the agglomeratesdescribed above. Typically, a residence time of up to about 120 seconds,preferably about 40-60 seconds is preferred, but this can changedepending on the type of segments being processed, other machinevariables and the desired size and/or shape of the finishedagglomerates. While declinations up to 10 degrees are possible, lowerdeclinations of up to about 5 or 6 degrees are more typical. With a 36inch diameter VibraDrum®, a preferred declination angle is about 4.5degrees. The vibration frequency can be varied to produce the waveaction by changing the RPM's of the vibrator motors that are typicallyvariable speed motors. Vibration frequencies in the range of about 500to about 1200 RPM are normally suitable to achieve the wave action. Atypical vibration frequency on a 36 inch diameter unit is in the rangeof about 875-925 RPM with a range of about 885-905 RPM, such as about890-895. A frequency of 893 RPM proved especially effective with amoisture content of 12.5-13.5 wt. percent and a declination angle ofabout 4:5 degrees on a 36 inch diameter by 10 foot long VibraDrum® unit.

One possible modification is shown in FIG. 5 which is a partial crosssection down the length of an elongated curved wave chamber 80. Aconcave working surface 83 is vibrated to act on wet chopped strandsegments to agglomerate them. The chamber 80 has a cover 82 that can bea straight plate or a slightly curved convex plate as shown in FIG. 5 orcan be slightly curved concave. The wave chamber 80 also has a framepiece 84A attached to a top of one side and a second frame piece 84Battached to the top of the other side. The wave chamber 80 and framepieces 84A and 84B are supported and vibrated in a same or similarmanner as the cylindrical wave chamber 52 shown in FIGS. 3 and 4.

Another possible modification is shown in FIG. 6 which is a partialcross section taken along the length of an elongated curved wave chamber86. A concave working surface 87 is vibrated to act on wet choppedstrand segments to agglomerate them. The chamber 86 has a cover 88 thathas at least two straight pieces 89 and 90 that intersect and join at anangle 91 as shown in FIG. 6. The wave chamber 86 also has a frame piece92A attached to a top of one side and a second frame piece 92B attachedto the top of the other side. The wave chamber 86 and frame pieces 92Aand 92B are supported and vibrated in a same or similar manner as thecylindrical wave chamber 52 shown in FIGS. 3 and 4.

A still further modification is shown in FIG. 7, a partial cross sectionalong the length of an elongated curved wave chamber 94. A concaveworking surface 95 is vibrated to act on wet chopped strand segments toagglomerate them. The wave chamber 94 has no cover, but instead is opento the atmosphere. An optional hood (not shown) could be mounted overthe open top of the wave chamber 94 to catch and remove any fibers ormoisture escaping out of the open top of the wave chamber 94 if desired.The wave chamber 94 also has a frame piece 96A attached to a top of oneside and a second frame piece 96B attached to the top of the other side.The wave chamber 94 and frame pieces 96A and 96B are supported andvibrated in a same or similar manner as the cylindrical wave chamber 52shown in FIGS. 3 and 4.

The radius of the curved working surface need not be constant as FIGS. 9and 10 illustrate. A working surface 97 in FIG. 9 has two radii and aworking surface in FIG. 10 has more than two radii.

On all of the many wave chamber devices disclosed above, the location ofthe vibrators and the array of coil springs between the vibrators andthe wave chamber can be changed. For example, the elongated curvedsurface wave chamber can be supported on each side with coil springsmounted on a supporting frame and the array of coil springs, box channeland opposed vibrators can be attached to the wave chamber near the topof the wave chamber. The only critical requirement is an elongatedcurved working concave surface acted upon to produce a wave-like motionon chopped strand segments and agglomerates contacting the concavesurface.

To practice the present invention using a system of the presentinvention as disclosed above, including the disclosure of FIGS. 2-4,conventional wet chopped fiber strand segments containing a conventionalsizing for a plastic material and a moisture content in the range ofabout 10 to about 16 wt. percent, on a dry basis, and chopped intosegments with any conventional chopper, such as shown in parts A and Bof FIGS. 1 and 2, are fed into an entry port of an agglomeratorcontaining an elongated curved surface wave chamber such as theVibraDrum® device shown in FIGS. 3 and 4. The angle of declination andthe feed rate are adjusted to produce a retention time in theagglomerator of between about 1-3 minutes. The actual feed rate, angleof declination and frequency will vary depending on the size of the wavechamber and the type of wet chopped strand segments being agglomeratedand the agglomerate size desired.

The amplitude of vibration of the wave chamber can also be varied toproduce the desired wave action and agglomerate size. Typically, anamplitude of about 0.625 inch is used, but this can be varied up or downas desired.

A retention time longer than about 120 seconds, more typically longerthan about 40-60 seconds could be used, but the minimum retention timeto achieve the agglomerate size desired is best to avoid possible damageto the fibers, especially on the outside layer of the agglomerates. Thelength of the chamber will also affect retention time and capacity ofthe wave chamber. Normally, the length of the wave chamber is fixed oncea unit is installed. Wave chambers about 4 feet long and about 8 feetlong are known to be satisfactory and no reason is known why otherlengths, within reason, would not also be suitable.

If the agglomerates are larger than desired, several things can be doneto reduce the agglomerate size as discussed above. Another thing thatcan be done to reduce agglomerate size is to reduce the moisture contentof the chopped strand segments before they are fed into the wavechamber. This may require some drying of the segments between thechopper and the wave chamber because the addition of more water and/orsizing to the segments after chopping is not required in the presentprocess.

The wet agglomerates 26 are fed into a dryer such as the conventionalvibrating, fluid bed dryer shown in part D of FIGS. 1 and 2, andpreferably processed with a conventional screen sorter shown as part Ein FIGS. 1 and 2 to produce finished agglomerated chopped fiber strandreinforcement product. Typical moisture contents of the wet choppedfiber strand segments coming from the chopper are in the range of about10 to about 15 wt. Percent, on a dry basis, i.e. based on the wt. of thedried segments.

The agglomerated chopped fiber strand reinforcement product produced inthe present system and by the present method had substantially improvedbulk density and flow characteristics compared with conventionalnon-agglomerated chopped fiber strand reinforcement products, andapparently similar characteristics as competitive agglomerated choppedfiber strand reinforcement products.

For example, conventional wet chopped fiber strand segments having amoisture content of 12 to 13.5 wt. percent, on a dry basis, were passedthrough the wave chamber device having an internal diameter of about 24inches, shown in FIGS. 3 and 4, at vibration frequencies of 700 to 900RPM and then run through parts D and E of the process shown in FIG. 2 toform dry agglomerated chopped fiber strand reinforcement products. Theresidence time in the wave chamber device was about 2 minutes, plus orminus 1 minute and the angle of declination was about 2 degrees. Twoconventional agglomerated products were made as described just above,one from ⅛ inch long chopped strand containing a first conventionalsizing and one from 3/16 inch long chopped strand containing a secondconventional sizing. The resultant agglomerated products were labeledProduct XA and Product XB respectively. Some key characteristics ofthese agglomerated products were measured and compared with results fromthe same tests on products made by passing the same conventional wetchopped fiber strand segments through parts D and E of the system shownin FIG. 2 and labeled CSA and CSB respectively.

The test results are shown below. Product Bulk Volume* Tapped Volume*Flow (Seconds)** XA 170 132 67 CSA 226 144 248 XB 160 128 111 CSB 196140 328*Volume in cubic centimeters per 500 gram sample.**Flow was determined by timing how long it took a 2000 gram sample toflow through an FMC FM-T01-A-1 vibrating hopper having a 1½ inchdiameter × 6 inch straight outlet.

The higher bulk density of the agglomerated products result in beingable to either place more weight in the standard sized box or otherpackage or allow a smaller package to be used to ship the same weight asused for the conventional chopped fiber strand products and also allowmore product to be stored in available space in the manufacturer's plantand in the customer's plant. The faster flow of the agglomeratedproducts result in fewer plug-ups in the customers' hoppers and feedtubes and in increased flow rates through existing customer equipmentthus removing this equipment where that is the barrier to increasedproduction rates.

While only preferred embodiments have been disclosed in detail above,many additional embodiments are possible and obvious to one of ordinaryskill given the above disclosure and the claims are intended to includesuch embodiments and obvious equivalents thereof. Agglomeratingparameters may have to be changed with some sizing compositions, but itwill be within the skill of an ordinary artisan, given the abovedisclosure, to use the above disclosed invention to agglomerate wetchopped strands having all kinds of sizing compositions on the surfaceof the fibers.

1-36. (canceled)
 37. A method of agglomerating chopped bundles of wetfiberglass strands into uniform segments, comprising: providing acontainer having a curved inner surface disposed about a generallyhorizontally extending longitudinal axis, mounting the container on aplurality of springs to resiliently support the container above a basesurface therefore, placing a plurality of chopped bundles of wetfiberglass strands to be agglomerated onto the curved inner surface atan input end of the container, producing vibratory force to cause thechopped bundles of wet fiberglass strands to move from the input end toan output end of the container, the vibratory force causing the choppedbundles of wet fiberglass strands to be directed in a rising and fallingpath of rolling movement, whereby the rolling movement of the choppedbundles produces uniform segments by causing agglomeration of the wetfiberglass strands.
 38. The method of claim 37 wherein the container isin the form of a cylindrical drum and a dimpled liner is provided withinthe cylindrical drum to define the curved inner surface upon which thechopped bundles of fiberglass strands undergo rolling movement.
 39. Themethod of claim 38 wherein the curved inner surface defined by thedimpled liner within the cylindrical drum includes a plurality ofgenerally elongated dimples projecting inwardly in relation to thecylindrical drum so as to be staggered in adjacent rows.
 40. The methodof claim 39 wherein the generally elongated dimples of the curved innersurface defined by the dimpled liner are generally elliptical and areelongated in the direction of the generally horizontally extendinglongitudinal axis of the container.
 41. The method of claim 37 whereinthe vibratory force which is produced is directed along a linear pathdisplaced from the generally horizontally extending longitudinal axisand also displaced from the center of gravity of the container.
 42. Themethod of claim 37 wherein the plurality of springs upon which thecontainer is mounted resiliently support the container above the basesurface for